Various systems operating within an industrial, commercial or residential environment that detect, and take autonomous action in response to, electrical distribution line disturbances have been around for many years. Grid operators are very interested in these types of devices since they can increase the reliability and stability of the power grid. The importance of detecting under-frequency, for example, which indicates a stressed grid, and responding by rapidly reducing load on the grid in order to stabilize the system, has been well documented (Pacific Northwest GridWise™ Testbed Demonstration Projects, Part II—Grid Friendly™ Appliance Project, under contract to Department of Energy, DE-AC05-76RL01830).
To date, solutions have typically been localized to individual energy consuming devices in an industrial, commercial, or residential building. For example, there are thermostats that can detect line disturbances based on anomalies in the 24VAC transformed power used by the thermostat electronics and delivered from a furnace system (U.S. Pat. No. 7,242,114). In some cases, they are further capable of running internal decision making algorithms, and then setting back the thermostat settings, or completely turning off a furnace or air conditioner. There are also grid friendly components that enable appliances to perform much the same action autonomously, based upon hard-coded parameters used to determine a line disturbance and effect load shedding. However, these products all require that each load control device that controls an energy consuming device, such as a thermostat for a heating ventilation and air conditioning (HVAC) system, refrigeration temperature control, water heater temperature control, lighting level control, baseboard heater control, etcetera employ line disturbance detection circuitry that can take autonomous action in response to the detected disturbance. Since these load control devices are often embedded within the energy consuming device they control, it is usually necessary to purchase a new appliance or piece of equipment that already employs the line disturbance detection circuitry. In new construction this may be cost-effective since new appliances and equipment are purchased and installed as part of the construction, although it is worth noting the extra cost of circuitry for detecting line disturbances burdens each appliance or piece of equipment. Replacing appliances or equipment in existing buildings with new appliances, or equipment employing line disturbance detection circuitry to provide load response sufficient to contribute to stabilizing the grid, is not cost effective.
There is need in the industry to provide local response to line disturbances without requiring that every piece of equipment under control be replaced with equipment employing line disturbance detection circuitry and relying on each of these to independently make a load reduction or addition decision. In particular, a central control point is needed that can detect line disturbances, quickly determine the proper course of action, and then communicate with load control devices that do not have line disturbance detection circuitry but can respond to a control directive from the central point of control.